Reservoirs are subterranean formations of rock containing oil, gas, and/or water. Unconventional reservoirs include coal and shale formations containing gas and, in some cases, water. A coal bed, for example, may contain natural gas and water.
Coal bed methane (CBM) is often produced using vertical wells drilled from the surface into a coal bed. Vertical wells drain a very small radius of methane gas in low permeability formations. As a result, after gas in the vicinity of the vertical well has been produced, further production from the coal seam through the vertical well is limited.
To enhance production through vertical wells, the wells have been fractured using conventional and/or other stimulation techniques. Horizontal patterns have also been formed in coal seams to increase and/or accelerate gas production.